The present invention relates to a resin composition and a film thereof, which is low in glossiness, low in transparency, superior in tear strength, of pliable silk cloth-like feel, and low in loudness when crumpled by hands.
Many of polyethylene films used as materials for packaging have high glossiness to obtain a superior appearance, high transparency to make packaged goods visible, as well as physical properties such as superior tear strength.
However, depending upon application purposes, the glossiness and high-transparency are not required. When used for the packaging of sanitary goods such as tissue paper, diaper paper and other goods, such as disposable rain wears and medical sheets, and polyethylene gloves used in places such as kitchens, factories, food stores, hotels"" and hospitals, a polyethylene film is desired to be superior in tear strength, and in addition to, low glossiness, low transparency, a pliable silk cloth-like feel, and low loudness when crumpled by hand.
With respect to resin compositions and films with which the present invention is concerned, JP-A 61-106645 discloses a film of a mixture of ethylene-vinyl acetate copolymer and polyethylene; JP-A 2-4846 discloses a film of a mixture of ethylene-(meth)acrylate copolymer and polyethylene; JP-A 7-292174 discloses a resin composition comprising ethylene-1-hexene copolymer obtained by using a metallocene catalyst and ethylene-vinyl acetate copolymer, and a film of said resin composition; and JP-A 8-283480 discloses a resin composition comprising ethylene copolymer obtained using a metallocene catalyst, ethylene-vinyl ester copolymer and an anti-blocking agent.
However, the films disclosed in JP-A 61-106645 and JP-A 2-4846 are not satisfactory with respect to the low-glossiness, low-transparency and tear strength, and the films of the resin compositions disclosed in JP-A 7-292174 and JP-A 8-283480 are too transparent.
An object of the present invention is to provide a film, which is low in glossiness, low in transparency, superior in tear strength, pliable with a silk cloth-like feel, and low in loudness when crumpled by hands.
Another object of the present invention is to provide a resin composition capable of providing such a film.
The present invention provides a resin composition comprising;
(A) from 1 to 99% by weight of a copolymer, which comprises an ethylene unit and an a-olefin unit of 3 to 12 carbon atoms and,
(B) from 99 to 1% by weight of a copolymer, which comprises an ethylene unit and a unit of a compound having a carbon-carbon double bond and an oxygen atom, provided that the sum of the copolymer (A) and the copolymer
(C) is 100% by weight, wherein the copolymer (A) satisfies the following requirements (A-1) to (A-4), and the copolymer (B) satisfies the following requirements (B-1) and (B-2),
(A-1): a melt flow rate (MFR) is from 0.1 to 50 g/10 min,
(A-2): a density (d) is from 880 to 935 Kg/m3,
(A-3): a composition distribution variation coefficient (Cx) represented by the following equation (1) is not more than 0.5,
xe2x80x83Cx="sgr"/SCBavexe2x80x83xe2x80x83(1)
wherein "sgr" is a standard deviation of composition distribution, and SCBave is an average branching degree,
(A-4): a content (a) of cold xylene-soluble portion in terms of % by weight based on the weight of the copolymer (A) and the density (d) satisfy the following inequality (2),
a less than 4.8xc3x9710xe2x88x925xc3x97(950xe2x88x92d)3+10xe2x88x926xc3x97(950xe2x88x92d)4+1xe2x80x83xe2x80x83(2).
(B-1): a melt flow rate (MFR) is from 0.01 to 50 g/10 min, and
(B-2): a content (b) of a unit of a compound having a carbon-carbon double bond and an oxygen atom in terms of % by weight based on the weight of the sum of the ethylene unit and the unit of a compound having a carbon-carbon double bond and an oxygen atom, and a content (WB) of the copolymer (B) in the resin composition in terms of % by weight based on the weight of the sum of the copolymer (A) and the copolymer (B) satisfy the following inequality (3),
50 greater than b greater than 0.2xc3x97WB+10xe2x80x83xe2x80x83(3).
The present invention also provides a film comprising the above-mentioned resin composition.
The copolymer (A) used in the present invention, which is, according to circumstances, referred to as xe2x80x9ccomponent (A)xe2x80x9d, can be obtained by copolymerizing ethylene and at least one xcex1-olefin of 3 to 12 carbon atoms. The above mentioned xe2x80x9cethylene unitxe2x80x9d means a structure unit derived from ethylene. Similarly, the above-mentioned xe2x80x9cxcex1-olefin unit of 3 to 12 carbon atomsxe2x80x9d means a structure unit derived from said a-olefin.
Examples of the above-mentioned xcex1-olefin are propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, dodecene-1, 4-methyl-pentene-1, 4-methyl-hexene-1 and vinylcyclohexane. Of these, preferred are butene-1, hexene-1 and octene-1, and more preferred is hexene-1.
Examples of the copolymer (A) are ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer and ethylene-octene-1 copolymer. Of these, ethylene-hexene-1 copolymer is preferred.
A melt flow rate (MFR) of the copolymer (A) is from 0.1 to 50 g/10 min, preferably from 0.5 to 20 g/10 min, more preferably from 0.5 to 10 g/10 min, much more preferably from 2 to 5 g/10 min. When the melt flow rate is less than 0.1 g/10 min, the film from the obtained resin composition may be too heavy. When it exceeds 50 g/10 min, tear strength of the film obtained may decrease.
A density (d) of the copolymer (A) is from 880 to 935 Kg/m3, preferably from 890 to 930 Kg/m3, more preferably from 910 to 930 Kg/m3. When the density is less than 880 Kg/m3, rigidity of the film obtained may decrease, and as a result, the film may become unsuitable for packaging film from a viewpoint of a handling facility. When it exceeds 935 Kg/m3, impact strength of the film obtained may decrease.
A composition distribution variation coefficient (Cx) represented by the above-mentioned equation (1) is not more than 0.5, preferably from 0.2 to 0.4. When the composition distribution variation coefficient exceeds 0.5, glossiness of the film in accordance with the present invention may increase, or tear strength and anti-blocking property thereof may deteriorate.
The composition distribution variation coefficient is a measure showing a distribution degree of the monomer unit in the copolymer (A). The smaller the Cx value, the narrower the composition distribution, in other words, the ethylene unit and the xcex1-olefin unit are more uniformly distributed in the copolymer (A). A measurement method of the Cx value is mentioned hereinafter.
A content (a) (% by weight) of cold xylene-soluble portion and a density (d) of the copolymer (A) satisfy the above-mentioned inequality (2). A copolymer (A) satisfying the following inequality (4) is preferred, and a copolymer (A) satisfying the following inequality (5) is more preferred.
a less than 4.8xc3x9710xe2x88x925xc3x97(950xe2x88x92d)3+10xe2x88x926xc3x97(950xe2x88x92d)4xe2x80x83xe2x80x83(4)
a less than 4.8xc3x9710xe2x88x925xc3x97(950xe2x88x92d)3xe2x80x83xe2x80x83(5)
When the copolymer (A) does not satisfy the above inequality (2), tear strength of the film in accordance with the present invention may decrease, glossiness thereof may increase or anti-blocking property thereof may deteriorate.
A process for producing the copolymer (A) is not limited. The copolymer (A) can be produced according to a conventional process using a conventional catalyst. As the conventional catalyst, those containing a transition metal compound be used. A preferred conventional catalyst is that which contains a transitional metal compound having a cyclopentadiene type anion skeleton-carrying group, namely, a so-called metallocene compound. A more preferred metallocene compound is represented by the following formula,
MLcXnxe2x88x92o
wherein M is a transition metal atom belonging to the group 4 or-the lanthanide series of the periodic table, L is a cyclopentadiene type anion skeleton-carrying group or a hetero atom-containing group, provided that at least one L is a cyclopentadiene type anion skeleton-carrying group, and plural L groups may be cross-linked with one another, X is a halogen atom or a hydrocarbon group of 1 to 20 carbon atoms, n is a valence of the transition metal atom, and c is an integer satisfying 0 less than cxe2x89xa6n.
The above-mentioned transition metal compound may be used individually or in a mixture of two or more.
The above-mentioned catalyst containing the transition metal compound can be obtained by combination (1) to combination (4).
(1) A combination of the transition metal compound with an organoaluminum compound such as triethylaluminum and triisobutylaluminum.
(2) A combination of the transition metal compound with an almoxane compound such as methylalmoxane.
(3) A combination of the transition metal compound, an organoaluminum compound such as triethylaluminum and triisobutylaluminum, and an ionic compound such as tolytyltetraxispentafluorophenyl borate and N,N-dimethylanilium tetraxispentafluorophenyl borate.
(4) A combination of the transition metal compound, an almoxane compound such as methylalmoxane, and an ionic compound such as tolytyltetraxispentafluorophenyl borate and N,N-dimethylanilium tetraxispentafluorophenyl borate.
Such a catalyst may be supported on a carrier comprising particulate inorganic carriers such as SiO2 and A12O3, and particulate organic polymers such as polyethylene and polystyrene.
As a polymerization method of the copolymer (A), for example, solution polymerization, slurry polymerization, high-pressure ion polymerization and gas phase polymerization methods may be used. Of these, gas phase polymerization and high-pressure ion polymerization methods are preferred.
The xe2x80x9ccopolymer (B) comprising an ethylene unit and a unit of a compound having a carbon-carbon double bond and an oxygen atom andxe2x80x9d used in the present invention, which is, according to circumstances, referred to as xe2x80x9ccomponent (B)xe2x80x9d, means a copolymer comprising an ethylene unit and a structure unit derived from a compound having a carbon-carbon double bond and an oxygen atom, which compound is copolymerizable with ethylene.
Examples of the compounds providing the unit of a compound having a carbon-carbon double bond and an oxygen atom are xcex2-unsaturated carboxylic acid alkyl esters such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate; carboxylicacidvinyl esters such as vinyl acetate, vinyl propionate, vinyl butanate and vinyl benzoate; and vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and phenyl vinyl ether. Of these, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and vinyl acetate are preferred.
A melt flow rate of the copolymer (B) is from 0.01 to 50 g/10 min, preferably from 0.1 to 20 g/10 min, more preferably from 1.5 to 10 g/10 min. When the MFR is less than 0.01 g/10 min, its compatibility with the copolymer (A) may deteriorate. When it exceeds 50 g/10 min, tear strength of the film in accordance with the present invention may decrease.
A content (b) (% by weight) of a unit of a compound having a carbon-carbon double bond and an oxygen atom in the copolymer (B), and a content (WB) (% by weight) of the copolymer (B) in the resin composition in accordance with the present invention must satisfy the above inequality (3), preferably the following inequality (6), wherein b (% by weight) is based on 100% by weight of the sum of a content of an ethylene unit and a content of a unit of a compound having a carbonxe2x80x94carbon double bond and an oxygen atom, and WB (% by weight) is based on 100% by weight of the sum of contents of the copolymers (A) and (B) in the resin composition in accordance with the present invention.
xe2x80x8350 greater than b greater than 0.7xc3x97WB+10xe2x80x83xe2x80x83(6)
A value of b (% by weight) is less than 50% by weight as shown in the above inequalities (3) and (6), preferably not more than 40% by weight, more preferably not more than 30% by weight. When the value of b is not less than 50% by weight, tear strength of the film in accordance with the present invention may decrease. On the other hand, the value of b exceeds 0.2xc3x97WB+10, preferably 0.7xc3x97WB+10. When the value of b is not more than 0.2xc3x97WB+10, glossiness of the film in accordance with the present invention may increase.
A process for producing the copolymer (B) is not particularly limited. For example, ethylene and the compound having at least one carbon-carbon double bond and an oxygen atom are subjected to copolymerization in the presence of a radical generator under conditions of from 50 to 400 MPa and from 100 to 300xc2x0 C., and, if desired, in the presence of a solvent and a chain transfer agent, which is called a high-pressure radical polymerization method. An average molecular weight of the copolymer (B) and contents of respective units contained in said copolymer can be controlled by adjusting the polymerization conditions.
The resin composition in accordance with the present invention comprises from 1 to 99% by weight of the copolymer (A) and from 99 to 1% by weight of the copolymer (B), preferably from 60 to 99% by weight of the copolymer (A) and from 40 to 1% by weight of the copolymer (B), more preferably from 70 to 99% by weight of the copolymer (A) and from 30 to 1% by weight of the copolymer (B), much more preferably from 85 to 994 by weight of the copolymer (A) and from 15 to 1% by weight of the copolymer (B), provided that the sum of the copolymer (A) and the copolymer (B) is 100% by weight.
When the content of the copolymer (A) is less than 1% by weight, glossiness of the film comprising the resin composition may increase, or impact strength thereof may decrease. When the content of the copolymer (A) exceeds 99% by weight, glossiness of said film may increase, or a film of pliable silk cloth-like feel may not be obtained.
The film in accordance with the present invention is a non-oriented film obtained by using the resin composition in accordance with the present invention. The film in accordance with the present invention has a haze value (an index of non-transparency) of preferably more than 20%, more preferably not less than 30%. The film in accordance with the present invention has a gloss value (an index of glossiness) of preferably less than 30%, more preferably not more than 25%, much more preferably not more than 15%.
A process for producing the resin composition in accordance with the present invention is not particularly limited. For example, the resin composition can be obtained according to a conventional blending method. According to the conventional blending method, for example, the copolymer (A) and the copolymer (B) are subjected to dry blend using a blender such as Henschell mixer and a tumbler mixer, or to melt blend using a mixer such as a single screw extruder, a twin screw extruder, Bumbury""s mixer and a hot roll.
A process for producing the film in accordance with the present invention is not particularly limited, and may be a conventional one. As the conventional process, a tubular film process using a tubular film forming apparatus and a T die casting process using a T die cast film forming apparatus can be used. Of these, a tubular film process is preferred.
The film in accordance with the present invention can be used as at least one side surface layer of a multi-layer film. As materials of the other layer (substrate) constituting the multi-layer film, for example, cellophane, paper, cardboard, cloth, aluminum foil, polyamide resin such as nylon 6 and nylon 66, polyester resin such as polybutylene terephthalate polybutylene terephalate, and oriented polypropylene may be used.
A process for producing said multi-layer film is not particularly limited, and may be a conventional one. A process wherein the resin composition in accordance with the present invention and the above-mentioned material for the substrate are subjected to co-extrusion or extrusion coating, wherein the latter process is also called an extrusion laminating process. Alternatively, the multi-layer film can be obtained, for example, by laminating the film in accordance with the present invention (single layer film) on the above-mentioned substrate according to lamination processes such as dry lamination, wet lamination, sandwich lamination and hot melt lamination.
The film in accordance with the present invention and the above-mentioned multi-layer film can be particularly suitably used as materials for producing a film used for packaging sanitary goods such as tissue paper, paper diaper and goods of the body, and materials for producing a glove readily used in places such as kitchens, factories, food stores, hotels and hospitals.
A process for producing a glove is not particularly limited. For example, the glove can be produced according to a conventional process wherein two sheets of the film are placed one over the other, thereafter the periphery of the superimposed is heat-melt-bonded along a shape of hand, and then a portion corresponding to a wrist is made open.
If desired, the components (A) and (B) used in the present invention may be used in combination with additives such as antioxidants, lubricants, antistatic agents, processing improvers and anti-blocking agents.
Examples of the antioxidants are phenol antioxidants such as 2,6-di-t-butyl-p-cresol(BHT), tetraxis [methylene-3-(3,5-di-t-butyl-4-hydroxy-henyl) propionate]methane (a trade mark of IRGANOX 1010, manufactured by Ciba Specialty Chemicals K.K.) and n-octadecyl-3-(4xe2x80x2-hydroxy-3,5xe2x80x2-di-t-butylphenyl)propionate (a trade mark of IRGANOX 1076, manufactured by Ciba Specialty Chemicals K.K.); and phosphite antioxidants such as bis(2,4-di-t-butylphenyl)pentaerythritoldiphosphite and tris(2,4-di-t-butylphenyl)phosphite.
Examples of the lubricants are erucic amide, higher fatty acid amides and higher fatty acid esters. Examples of the antistatic agents are glycerol C8 to C22 fatty acid ester, sorbitan C8 to C22 fatty acid ester and polyethylene glycol C8 to C22 fatty acid ester. Examples of the processing improvers metal salts of fatty acids such as calcium stearate. Examples anti-blocking agents are silica, diatomaceous earth, calcium carbonate and talc.
A process for combining the copolymer (A) and the copolymer (B) with the additive is not limited. For example, the additive is added to a mixture of the copolymer (A) and the copolymer (B), or separately added to each one of the copolymer (A) and the copolymer (B). Alternatively, the additive may be added to a master batch of the copolymer (A) or the copolymer (B).